Efficient IGBT switching

ABSTRACT

Embodiments of the invention provide IGBT circuit modules with increased efficiencies. These efficiencies can be realized in a number of ways. In some embodiments, the gate resistance and/or voltage can be minimized. In some embodiments, the IGBT circuit module can be switched using an isolated receiver such as a fiber optic receiver. In some embodiments, a single driver can drive a single IGBT. And in some embodiments, a current bypass circuit can be included. Various other embodiments of the invention are disclosed.

BACKGROUND

The Insulated Gate Bipolar Transistor (IGBT) is a minority-carrierdevice with high input impedance and large bipolar current-carryingcapability. Many designers view IGBTs as devices with MOS inputcharacteristics and bipolar output characteristics that arevoltage-controlled bipolar devices. The IGBT is a functional integrationof Power MOSFET and BJT devices in monolithic form and combines the bestattributes of both to achieve optimal device characteristics.

The IGBT is suitable for many applications in power electronics,especially in Pulse Width Modulated (PWM) servo and three-phase drivesrequiring high dynamic range control and low noise. It also can be usedin Uninterruptible Power Supplies (UPS), Switched-Mode Power Supplies(SMPS), and other power circuits requiring high switch repetition rates.IGBT improves dynamic performance and efficiency and reduces the levelof audible noise. It is equally suitable in resonant-mode convertercircuits. Optimized IGBTs are available for both low conduction loss andlow switching loss.

SUMMARY

Embodiments of the invention provide IGBT circuit modules with improvedefficiencies. These efficiencies can be realized in a number of ways. Insome embodiments, the gate resistance and/or inductance can beminimized. In some embodiments, the IGBT circuit module can be switchedusing an isolated receiver such as a fiber optic receiver. In someembodiments, a single driver can drive a single IGBT. And in someembodiments, a current bypass circuit can be included. Various otherembodiments of the invention are disclosed.

The terms “invention,” “the invention,” “this invention” and “thepresent invention” used in this patent are intended to refer broadly toall of the subject matter of this patent and the patent claims below.Statements containing these terms should be understood not to limit thesubject matter described herein or to limit the meaning or scope of thepatent claims below. Embodiments of the invention covered by this patentare defined by the claims below, not this summary. This summary is ahigh-level overview of various aspects of the invention and introducessome of the concepts that are further described in the DetailedDescription section below. This summary is not intended to identify keyor essential features of the claimed subject matter, nor is it intendedto be used in isolation to determine the scope of the claimed subjectmatter. The subject matter should be understood by reference toappropriate portions of the entire specification of this patent, and orall drawings and each claim.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments of the present invention are described indetail below with reference to the following figures:

FIG. 1 is a circuit diagram of an IGBT circuit module according to someembodiments of the invention.

FIG. 2 shows a receiver and pre-driver circuit and an IGBT circuitaccording to some embodiments of the invention.

FIG. 3 is a graph of the rise time of the voltage at the gate and therise time of the current through an IGBT according to some embodimentsof the invention.

FIG. 4 is a graph of the current rise time and the fall time of thevoltage at the collector and emitter according to some embodiments ofthe invention.

FIG. 5 is a graph of the current rise time at the current bypass circuitand the fall time of the voltage at the collector and emitter accordingto some embodiments of the invention.

FIG. 6A is a graph of the collector current and the voltage between thecollector and emitter for a standard IGBT.

FIG. 6B is a graph of the collector current and the voltage between thecollector and emitter for an IGBT circuit module according toembodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The subject matter of embodiments of the present invention is describedhere with specificity to meet statutory requirements, but thisdescription is not necessarily intended to limit the scope of theclaims. The claimed subject matter may be embodied in other ways, mayinclude different elements or steps, and may be used in conjunction withother existing or future technologies. This description should not beinterpreted as implying any particular order or arrangement among orbetween various steps or elements except when the order of individualsteps or arrangement of elements is explicitly described. Like numeralswithin the drawings and mentioned herein represent substantiallyidentical structural elements. Each example is provided by way ofexplanation, and not as a limitation. For instance, features illustratedor described as part of one embodiment may be used on another embodimentto yield a further embodiment. Thus, it is intended that this disclosureincludes modifications and variations.

Embodiments of the invention include power supply modules withinsulated-gate bipolar transistors (IGBT) that operate with improvedefficiencies. These modules can include IGBT circuit modules that canproduce high power output (e.g., above 100 kW) with little power loss.Each circuit module can include a single IGBT. Multiple circuit modulesmay be configured in parallel and/or series configurations. Among otherefficiencies, these efficiencies can be realized with decreased turn-ontimes and/or turn-off times as well as lowering losses during switching.Although these efficiencies may be incremental for each individualcycle, when aggregated over many IGBT circuit modules and over the manycycles per second, such efficiencies can result in significant powersavings.

Embodiments of the invention can be used in a number of applications. Inparticular, these devices can be used with solar panels, solar farms,windmills, hydroelectric facilities, coal power facilities, powertransmission, power conversion, electric vehicles, air planes, and/orsatellites. IGBT modules disclosed here in can provide value addedfunctions such as frequency regulation, renewable firming, power qualityenhancement, and/or dynamic stability support. Often power conversionsystems can be a source of power loss. Improvements to power conversionsystems will improve the efficiencies of the system. Any such efficiencyimprovements will lessen the environmental impact on the system as awhole. Thus embodiments of the invention are a green technologysolution.

IGBT manufacturers produce a variety of IGBTs with different operatingcharacteristics that require various design considerations. Despitethese various characteristics, embodiments of the invention can be usedwith any type of IGBT. Embodiments of the invention can be used withdiscrete and/or brick IGBTs. Typically, IGBTs include manufacturerspecifications that include such things as rise time, turn-on delaytime, turn-off delay time, various operating voltages and currents,turn-on switching loss, delay times, and/or turn-off switching loss toname a few. In many instances, embodiments of the invention push IGBTsbeyond or up to the manufacturer's specifications to obtain improvedefficiencies. One example of an IGBT is model number IRGPS40B120UPmanufactured by International Rectifier.

FIG. 1 is a circuit diagram of IGBT circuit module 100 according to oneembodiment of the invention. IGBT circuit module 100 includes IGBT 114along with a number of components arranged to ensure fast and/or moreefficient switching of load 130. Circuit module 100 shows a number ofelements that can vary in location, combination, value, and/orconfiguration. Indeed, some elements can be replaced or removed. Othersrepresent inherent characteristics of the circuit module and/or circuitcomponents such as trace resistance and/or component inductance.Elements representing inherent characteristics may not be actualphysical components. Instead, these elements are shown simply fordiscussion purposes and/or to describe that such characteristics may bepresent.

Receiver 102 is coupled to an external input and receives inputswitching signals. While receiver 102 is coupled with a 5 volt powersupply any type of receiver operating at any voltage or power level maybe used. Receiver 102 can be isolated from the environment and/or fromthe remaining circuitry in a number of ways. For example, receiver 102can be a fiber optic receiver that allows each IGBT module 100 to floatrelative to other IGBT modules or other circuitry. Individual modulegrounds can be isolated from one another, for example, using anisolation transformer. Electrical isolation of IGBT module 100 can allowmultiple IGBT circuit modules to be arranged in a series configurationfor high voltage switching. Fiber optic receivers can also be used toreduce switching noise.

Pre-driver 104 and gate driver 106 can provide large current pulsesgreater than 10 amps and continuous current greater than 2 amps to IGBT114. These drivers can be any of high speed, high current driversdesigned for use with either MOSFETs and/or IGBTs. For example, thesedrivers can be any low-side ultrafast driver manufactured by IXYSCorporation (e.g., IXYS #IXDN430 or IXYS #IXDN630).

Pre-driver 104 is electrically coupled with the output of receiver 102and the output of pre-driver 104 is electrically coupled with gatedriver 106 resulting in a dual-driver configuration. In theconfiguration shown, these drivers are coupled with a 35 volt powersupply, although any power supply will work. Moreover, these drivers maynot be coupled with the same power supply. While fiber optic receiver102, pre-driver 104 and gate driver 106 are shown, various otherreceiver and driver combinations can be used such as, for example, asingle receiver coupled with a single driver. In some configurations,pre-driver 104 and receiver 102 can be included on receiver circuitmodule 105 separate from circuit module 107. In other configurations,these devices can be located on the same circuit module as IGBT 114 andother components. Furthermore, pre-driver 104 can be coupled in parallelwith a plurality of gate drivers that drive a plurality of IGBTs asshown in FIG. 2.

The output of gate driver 106 is electrically coupled with gate 132 ofIGBT 114. IGBT 114 can include internal emitter inductance (L_(e)) 115within effective IGBT 112. Resistance 108 and/or inductance 110 show theinternal resistance and/or inductance of the gate and may not be anadditional component, although an additional component may be used foreach. That is, the output of gate driver 106 can be directly coupledwith gate 132 of IGBT 114 using a circuit trace and/or an additionalcomponent and/or additional components. Typical IGBTs includespecifications that a gate resistor is required between gate driver 106and gate 132. Thus, the elimination of such a resistor is contrary totypical IGBT specifications.

Resistance 108 can be the effective internal resistance at the gate.This resistance can include the resistance of the trace between gatedriver 106 and IGBT 114 and/or any internal resistance within the gateof IGBT 114. Resistor 108 can have a resistance less than 2Ω, 1Ω, 500mΩ, 100 mΩ, 50 mΩ, 10 mΩ, or 1 mΩ. To achieve these low resistancelevels, the output of gate driver 106 and gate 132 of IGBT 114 can havea very short physical trace length. This distance can be, for example,less than 1 cm, 500 mm, 100 mm, 50 mm, 10 mm, or 1 mm.

Inductance 110 can represent the internal inductance of the gate. Thisinductance can include the inductance of the trace between gate driver106 and IGBT 114 and/or any internal inductance within the gate of IGBT114. Inductance 110 may or may not be an added component. Inductance 110can have an inductance less than 100 nH, 50 nH, 40 nH, 20 nH, 10 nH, 5nH, or 1 nH. To achieve these low inductance levels, the trace on thecircuit module connecting the output of gate driver 106 and IGBT 114 canhave a wide trace width. For example, this width can be greater than 1mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm.

IGBT 114 can include collector 134 and emitter 133. Emitter 133 iscoupled with a 10 volt bias voltage. In other embodiments, emitter 133can be coupled to other bias voltages including ground. Load 130 iscoupled with collector 134 and emitter 133.

Current bypass circuit 116 can be electrically coupled between emitter133 and collector 134. This bypass may include some circuit inductancerepresented by bypass inductance 120. Current bypass circuit 116 can bedesigned to allow for an easy current bypass to IGBT 114. Capacitor 128can be included between emitter 133 and gate driver 106.

Snubber 118 can also be included between collector 134 and emitter 133.Snubber 118 may include additional components and/or connections.Moreover, Snubber 118 may or may not include connections at collector134 and/or emitter 133. Snubber 118 can include any type of snubbercircuitry known in the art. For example, snubber 118 can include a diodesnubber, RF snubber, solid-state snubber, or a combination of these. Forexample, snubber 118 can include a capacitor in series with a parallelconfiguration of a diode and a resistor. Snubber 118 can also includesnubber inductance 122 whether as part of snubber 118 or as inductancewithin the snubber circuit. Snubber 118 can be used to suppress voltagetransients across load 130 and/or absorb energy from stray circuitinductance to prevent over-voltage at IGBT 114. Current bypass circuit116 and snubber 118 can be included in a single circuit.

IGBT circuit module 100 can also include fast capacitor 126 and slowcapacitor 124 in parallel between collector 134 and load 130. Thesecapacitors can have inherent inductance represented by fast capacitorinductance 121 and slow capacitor inductance 123. In some embodiments,these inductances may result from actual inductors. In others, theseinductances may be inductances within the circuit and/or capacitors 124and 126. Fast capacitor 126 and/or slow capacitor 124 may be locatedexternally to IGBT circuit module 100, and/or may span multiple IGBTcircuit modules, and may not connect to each IGBT circuit module.

Fast capacitor 126 can be in parallel with a main energy storagecapacitor (e.g., slow capacitor 124). Fast capacitor 126 may only storea small portion of the total energy required, which can allow it to besmaller, and/or be placed closer to the IGBT switch than main energystorage capacitor. In so doing, stray inductance between fast capacitor126 and IGBT 114 can be minimized. Fast capacitor 126 can absorb energystored in the stray inductance between itself and the main energystorage capacitor, which can reduce the energy dissipated in IGBT 114during switching.

Embodiments of the invention can allow for rapid IGBT gate charging. Forexample, gate 132 of IGBT 114 can be brought to the full IGBTmanufacture's specified Gate to Emitter Voltage (e.g., V_(GE)>20 volts)in a time (t_(vg)) less than the manufacturer-specified 10% to 90%current rise time (t_(r)) as shown in FIG. 3. Additionally embodimentsof the invention can allow for rapid IGBT discharging by reducing V_(GE)from the manufacture's specified on state voltage to less than or equalto zero in a time less than the manufacturer-specified 10% to 90%current rise time (t_(r)). These rise times can vary depending on theIGBT used. For some known IGBTs this current rise time, for example, canbe less than 50 ns, 40 ns, 30 ns, 20 ns, or 10 ns. Other rise times maybe used. Removal of the gate resistor is one design consideration thatproduces fast rise times. This can allow for a sufficiently large peakcurrent to flow to the gate to charge it more quickly than specified.The gate may still have some inherent circuit or trace resistance on theorder of less than about 2Ω. IGBT manufacturers typically suggest and/orrequire 5Ω as the minimum gate resistance. Thus, one embodiment of theinvention uses a gate resistance much less than the gate resistancerecommended by the IGBT manufacturer. Another embodiment of theinvention couples a driver with the gate without a resistortherebetween.

Use of a gate driver (e.g., gate driver 106) with a single discrete IGBTis another design consideration that can allow for fast rise times. Thatis, each of a plurality of IGBTs can be coupled with a single gatedriver. Typically, multiple discrete IGBTs or single IGBT modules thatinclude a plurality of IGBTs are coupled with a single driver. A gatedriver coupled only with a single discrete IGBT can generate the currentneeded to rapidly charge a single IGBT gate capacitance to themanufacturer's specified on state voltage level. (e.g., I_(g)>10 A).

Moreover, various combinations of IGBTs and drivers can be used. Forexample, a single IGBT can be coupled with multiple drivers. As anotherexample, multiple drivers and multiple IGBTs can be coupled together.Any number of combinations can be used.

The reduction of the IGBT gate inductance (e.g. inductance 110) to verylow values is another design consideration that can allow for fast risetimes (e.g., L_(g)<10 nH). The gate inductance initially acts as highimpedance from the driver output to the IGBT gate. The lower the valueof the gate inductance the faster the gate can be charged to fullvoltage. Various techniques are described in this disclosure forproducing low gate inductances.

Embodiments of the invention can also allow for a reduction of Collectorto Emitter Current (I_(CE)) during IGBT turn-on. In some embodiments,the current rise time (t_(r)) through the IGBT at turn-on can be slowerthan the time it takes to have the collector-to-emitter voltage (V_(CE))fall (t_(f)) from 90% to 10% of its value as shown in FIG. 4. That is,the voltage across the IGBT can go from high to low before the devicestarts to carry any significant current. This can make the device fasterand dissipate less energy during the switching process.

To accomplish current reduction during turn-on, a minimum circuitinductance can be required to effectively choke the current rise-time.This minimum circuit inductance can include any of the followingsingularly or in combination: IGBT internal emitter inductance (L_(e))115, stray inductance 136, slow capacitor inductance 123, and fastcapacitor inductance 121. Stray inductance 136 can include anyunaccounted-for inductance in IGBT circuit module 100 and/or anyinductance in load 130. This minimum inductance can be greater thanabout 50-100 nH. For example, the combination of stray inductance 136,fast capacitor inductance 121, and IGBT inductance can be between 50 and100 nH.

Embodiments of the invention can also allow for fast shunting of currentout of the IGBT 114 during device turn-off. This can be accomplishedusing, for example, current bypass circuit 116. To achieve effectivecurrent shunting, the time it takes for 50% of the current to bediverted out of IGBT 114 into current bypass circuit 116 can be lessthan the time it takes for IGBT 114 to turn off. That is, current bypasscircuit 116 can have a current rise time (t_(r)) that is faster than thespecified IGBT turn-off time (t_(f)) as shown in FIG. 5. This allows forvery low collector to emitter current in IGBT 114 during switching,which makes the device operate faster and/or dissipates less energyduring turn-off.

To ensure that current can be passed out of IGBT 114, current bypassinductance 120 can be required to be low enough to allow current to rampup quickly in the bypass circuit as the IGBT begins to switch. In someembodiments, current bypass circuit 116 can include a capacitor and/ordiode in an arrangement similar to a snubber, which can allow current toflow through current bypass circuit 116 until the capacitor is fullycharged. While current bypass circuit 116 is somewhat similar to atypical snubber, there are some differences.

Among many design considerations, typical snubbers can be designed toreduce and/or minimize voltage spikes across the IGBT that may occurduring switching. Their design can be based on circuit elements thatfall outside the loop formed by effective IGBT 112, current bypass 116and/or inductor 120, as well as by the properties of the circuit IGBT.Current bypass 116 can be designed to allow current to rapidlytransition from flowing through the IGBT to flowing through currentbypass 116, largely irrespective of other circuit elements. The designof circuit bypass 116 is largely based on circuit elements containedwithin the loop formed by effective IGBT 112, current bypass 116 andinductor 120, as opposed to those that lie outside of this loop, incontrast to the typical IGBT snubber 118. In some embodiments of theinvention current bypass inductance 120 is minimized to a value, forexample, below 20 nH or 10 nH. In some embodiments, the combination ofcurrent bypass inductance 120 and snubber inductance 122 can be lessthan 20 nH. With this low inductance, current can rapidly shunt throughcurrent bypass circuit 116. This shunting can occur in less than 100 ns,80 ns, 60 ns, 40 ns, 20 ns, or 10 ns. In some embodiments, currentbypass 116 may be combined with snubber 118.

In some embodiments, IGBT 114 can be operated above the manufacturespecified continuous collector current (I_(c)) level. This combined witha very low circuit inductance can allow for faster device turn-offtimes. In most power supply designs, operation above the manufacturedspecified continuous current level is avoided because high currentlevels can cause large voltage spikes that can damage the IGBTs.Additionally, high current levels can overheat the IGBTs. Moreover, itcan be considered poor circuit design to operate componentsabove/outside the manufacture's specifications.

It is well known that voltage across an inductor is equal to theinductance and the time rate of change of the current

$\left( {V = {L\frac{\mathbb{d}i}{\mathbb{d}t}}} \right).$If the circuit inductance is minimized to allow for a maximum ratechange of current during turn-off and a current level near, at or abovethe IGBT's specified continuous current rating is applied, voltage canbe developed across internal IGBT internal emitter inductance (L_(e))115. This induced voltage can help the device turn-off faster. Circuitinductance can include stray inductance 136 and/or fast capacitorinductance 121 and can have a value on the order of IGBT internalemitter inductance (L_(e)) 115. For example, stray inductance 136 and/orfast capacitor inductance 121 can be less than or equal to IGBTinductance 136. This effect can be seen at current levels near or abovethe IGBT's specified continuous current rating.

To avoid overheating when operating at current levels above themanufacturer's stated continuous maximum current, a plurality of IGBTcircuit modules can be combined in series or parallel that alternateswitching between IGBTs. By alternating switching, each IGBT can have acool-down period, while others IGBTs do the work. In some embodiments,each of two subsets of IGBTs can alternate switching. In otherembodiments, each of three or more subsets of IGBTs can alternateswitching.

In some embodiments, fast capacitor 126 can be coupled between load 130and IGBT 114. The inductance of this circuit is represented by fastcapacitor inductance 121, and can be very low (e.g., less than 50 nH).Capacitor inductor 121 can be the inherent or internal inductance offast capacitor 126 and/or the circuitry related to fast capacitor 126.

A low resistance between gate 132 and gate driver 106 can improve theswitching efficiency. This low resistance can be realized in a number ofways. In one embodiment, gate 132 can be electrically coupled with gatedriver 106 without an external resistor being placed in series betweenthe two components. That is, gate driver 106 and gate 132 can bedirectly coupled together through a single circuit trace. Of course,some resistance in the trace will be present, but this resistance willbe minimal (e.g., less than 0.1 ohms). In another embodiment, gatedriver 106 and IGBT 114 can be placed very near one another on thecircuit module. For example, this distance can be less than 1 cm, 500mm, 100 mm, 50 mm, 10 mm, 1 mm, etc. In yet another embodiment, the linetrace on the circuit module between gate driver 106 and gate 132 canhave a resistance less than 1Ω, 500 mΩ, 100 mΩ, 50 mΩ, 10 mΩ, 1 mΩ, etc.

IGBTs are typically operated with a Collector to Emitter Voltage(V_(CE)) lower than the Collector to Emitter Voltage specified by themanufacturer to avoid over voltage spikes during switching. In a circuitwith inductance, when current is changing over time the resultingvoltage is a function of the inductance and the rate of the currentchange over time

$\left( {V = {L\frac{\mathbb{d}i}{\mathbb{d}t}}} \right).$This voltage coupled with the operating voltage can produce voltagespikes above the tolerances of the IGBT. To mitigate these spikes,circuit designers usually slow the switching speed and/or drive the IGBTwith a voltage below tolerance to accommodate spikes. Embodiments of theinvention, however, include circuit modules that can switch at higherswitching speeds and/or be driven with voltages at or above themanufacturer specified Collector to Emitter Voltage.

This can be accomplished in a number of ways. One example is to lowerthe inductance at the gate. Lower inductances can allow for fasterswitching without inducing or increasing voltage spikes. To do this, thetrace between gate driver 106 and gate 132 can be shorter than standard(e.g., around 10 mm) and/or wider than standard (e.g., around 4 mm).This short and/or wide trace can lower both the inductance and theresistance of gate driver 106. Various trace lengths can be used, forexample, trace lengths less than 20 mm, 15 mm, 5 mm, 2 mm, or 1 mm canbe used. Various trace widths can be used, for example, trace widthsgreater than 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mmcan be used.

Various other inductance lowering techniques can be used. By employingthese techniques the inductance at the gate can be less than 100 nH, 50nH, 40 nH, 20 nH, 10 nH, 5 nH, or 1 nH. For example, multiple traces canbe run in various board layers, and/or on the underside of the board.

In another embodiment, the inductance of the entire circuit modulewithout the IGBT can be less than the inductance of the IGBT (e.g.,inductance 115). In yet another embodiment, the inductance of the gatecircuit is less than the inductance of the IGBT.

In some embodiments, a plurality of IGBT modules can be coupled togetherin series to provide higher voltage and/or parallel to provide highercurrent. For example, if each IGBT module can switch 1 kV, then 20 IGBTmodules can be coupled in series to switch 20 kV. Various otherconfigurations can also be used. A similar strategy can be employed forincreasing the current with a parallel configuration.

IGBT modules according to embodiments of the invention can have turn-ondelay times (t_(d(on))) and/or turn-off delay times (t_(d(off))) thatare shorter than the manufacture specified times. For example, an IGBTmodule can have a turn-on delay time (t_(d(on))) and/or a turn-off delaytime (t_(d(off))) that is less than half the manufactured specifiedtime. As another example, an IGBT module can have a turn-on delay time(t_(d(on))) and/or a turn-off delay time (t_(d(off))) that is less thanone-fourth the manufactured specified time.

FIG. 2 shows series configuration 200 with four IGBT modules 230, 231,232, and 233 in series with load 130. Each IGBT module includes receiver102, pre-driver 104, gate driver 106, and IGBT 114. Various othercomponents may be present such as snubber and/or current bypasscircuitry.

Each IGBT module can be electrically isolated from one another. Thisisolation can allow each IGBT to divide the load voltage among thecollector-to-emitter voltages of the four IGBT modules. Using a fiberoptic receiver for receiver 102, switching signals can be isolated fromone another. Moreover, each IGBT board can float relative to oneanother. That is, each board may be tied to an independent common 215.Common 215 can be isolated from the other commons using transformerisolation or other isolation techniques. In this way, each board onlyswitches its collector-to-emitter voltage. But the sum of thecollect-to-emitter voltages of all the IGBT modules will be the loadvoltage.

Power can be brought to each board at various levels. For example, powerinput 205 can be 5 volt power supply, power input 210 can be from a 35volt power supply, and power input 220 can be from a 10 volt powersupply.

Various other configurations of IGBT modules can be used. For example,series configuration 200 can include any number of IGBT modules coupledtogether in series. As another example, multiple series configurationscan be coupled together in parallel to allow for increased currentswitching. And as another example, multiple IGBT modules can beconfigured in parallel and then arranged in series.

FIG. 6A shows typical rise and fall times of an IGBT circuit. In thisexample, rise times of 100 ns and fall times of 400 ns are typical.These values may vary based on individual IGBTs.

As an IGBT switches open, the current waveform can often becharacterized as having a sharp fall in current, followed by a long slowdrop in the current to zero. This long slow current drop is often calledthe tail current. Some definitions of the IGBT turn off time includethis tail current, while others do not. In some embodiments of theinvention, both the fall time and/or the tail current can lowered tolevels below the manufactured specified levels.

Switching energy loss can be a significant source of power loss in IGBTswhere switching is defined by the time it takes to largely eithertransition the device from either the conducting or non-conductingstate, typically characterized as specified device rise/fall times. Forexample, the rise times can be specified by the amount of time it takesto rise from 10% to 90% or values. The fall times can be specified bythe amount of time it takes to fall from 90% to 10% of the full value.FIG. 6B shows rise and fall times from an IGBT circuit that implementsembodiments of the invention. Note that the rise time is below 40 ns andthe fall time is less than 100 ns. According to embodiments of theinvention, improved rise and fall times similar to those shown in FIG.6B may be obtained using the same IGBT having the rise and fall timesshown in FIG. 6A with the circuit module configuration disclosed herein.

The foregoing is provided for purposes of illustrating, explaining, anddescribing embodiments of the present invention. Further modificationsand adaptations to these embodiments will be apparent to those skilledin the art and may be made without departing from the scope or spirit ofthe invention. Different arrangements of the components depicted in thedrawings or described above, as well as components and steps not shownor described are possible. Similarly, some features and subcombinationsare useful and may be employed without reference to other features andsubcombinations. Embodiments of the invention have been described forillustrative and not restrictive purposes, and alternative embodimentswill become apparent to readers of this patent. Accordingly, the presentinvention is not limited to the embodiments described above or depictedin the drawings, and various embodiments and modifications can be madewithout departing from the scope of the claims below.

What is claimed is:
 1. An IGBT circuit module comprising: a circuitboard; an IGBT coupled with the circuit board having a gate, acollector, and an emitter; a driver coupled with the circuit board; aplurality of traces, wherein a first trace of the plurality of traceselectrically couples the gate and the driver; and a fast capacitorcoupled with the collector via an inductor of inductance less than 50nH, wherein the circuit module is configured to couple with a loadbetween the emitter and the collector.
 2. The IGBT circuit moduleaccording to claim 1, wherein the IGBT includes a manufacturer-specifiedcurrent rise time, and wherein the voltage at the gate is brought to afull voltage in a time less than the manufacturer-specified current risetime.
 3. The IGBT circuit module according to claim 1, wherein the IGBTincludes a manufacturer-specified current fall time, and wherein thevoltage at the gate is discharged in a time less than themanufacturer-specified current fall time.
 4. The IGBT circuit moduleaccording to claim 1, wherein the IGBT includes a manufacturer-specifiedcurrent rise time, and wherein the voltage between the collector and theemitter is brought to a minimum voltage in a time less than themanufacturer-specified current rise time.
 5. The IGBT circuit moduleaccording to claim 1, wherein the IGBT circuit module includes aninternal circuit module inductance that is greater than 50 nH.
 6. TheIGBT circuit module according to claim 5, wherein the internal circuitmodule inductance includes either or both an internal IGBT inductanceand a stray circuit module inductance.
 7. The IGBT circuit moduleaccording to claim 1, wherein the driver is coupled with a single IGBT.8. The IGBT circuit module according to claim 1, wherein the IGBT has amanufacturer-specified switching loss, and the switching loss of theIGBT circuit module is less than the manufacturer-specified switchingloss.
 9. The IGBT circuit module according to claim 1, wherein the IGBThas a manufacturer-specified rise time, and the rise time of the IGBTcircuit module is less than the manufacturer-specified rise time. 10.The IGBT circuit module according to claim 1, wherein the IGBT has amanufacturer-specified fall time, and the fall time of the IGBT circuitmodule is less than the manufacturer-specified fall time.
 11. The IGBTcircuit module according to claim 1, wherein the IGBT has a manufacturerspecified turn-on delay time, and the turn-on delay time of the IGBTcircuit module is less than the manufacturer specified turn-on delaytime.
 12. The IGBT circuit module according to claim 1, wherein the IGBThas a manufacturer specified turn-off delay time, and the turn-off delaytime of the IGBT circuit module is less than the manufacturer specifiedturn-off delay time.
 13. The IGBT circuit module according to claim 1,wherein the turn-off delay time is less than 100 ns.
 14. The IGBTcircuit module according to claim 1, wherein the turn-on delay time isless than 40 ns.
 15. An IGBT circuit module comprising: a circuit board;an IGBT coupled with the circuit board having a gate, a collector, andan emitter; a driver coupled with the circuit board; a plurality oftraces, wherein a first trace of the plurality of traces electricallycouples the gate and the driver; and a current bypass circuit betweenthe collector and the emitter, wherein the current bypass circuitincludes an inductance less than 10 nH.
 16. An IGBT circuit modulecomprising: a circuit board; an IGBT coupled with the circuit boardhaving a gate, a collector, and an emitter; a driver coupled with thecircuit board and a fiber optic receiver; and a plurality of traces,wherein a first trace of the plurality of traces electrically couplesthe gate and the driver, wherein the driver is coupled with a fiberoptic receiver.
 17. The IGBT circuit module according to claim 1,wherein the driver is coupled with a pre-driver.
 18. The IGBT circuitmodule according to claim 1, wherein the first trace has a length lessthan 1 cm.
 19. The IGBT circuit module according to claim 1, wherein thefirst trace has a length less than 100 mm.
 20. The IGBT circuit moduleaccording to claim 1, wherein the first trace has a length less than 10mm.
 21. The IGBT circuit module according to claim 1, wherein the firsttrace has an inductance less than 100 nH.
 22. The IGBT circuit moduleaccording to claim 1, wherein the first trace has an inductance lessthan 10 nH.
 23. The IGBT circuit module according to claim 1, whereinthe first trace directly couples the driver with the gate without anadditional component.
 24. The IGBT circuit module according to claim 1,wherein the first trace directly couples the driver with the gatewithout a resistor.
 25. An IGBT circuit module comprising: a circuitboard; an IGBT coupled with the circuit board having a gate, acollector, and an emitter; a driver coupled with the circuit board; aplurality of traces, wherein a first trace of the plurality of traceselectrically couples the gate and the driver, wherein the IGBT has anemitter inductance and a collector inductance, wherein the emitterinductance is greater than or equal to the collector inducance.
 26. AnIGBT circuit module comprising: a circuit board; an IGBT coupled withthe circuit board having a gate, a collector, and an emitter; a drivercoupled with the circuit board; a plurality of traces, wherein a firsttrace of the plurality of traces electrically couples the gate and thedriver, wherein the IGBT has an inductance that is greater than theinductance of the IGBT circuit module without the IGBT.
 27. An IGBTcircuit module comprising a plurality of IGBTs, wherein each IGBTincludes a gate, a collector, and an emitter; a receiver; a pre-drivercoupled with the receiver; and a plurality of gate drivers coupled withthe pre-driver, and wherein each of the plurality of gate drivers iscoupled with the gate of one of the plurality of IGBTs.
 28. The IGBTcircuit module according to claim 27, wherein the receiver comprises afiber optic receiver.
 29. The IGBT circuit module according to claim 27,wherein the receiver and pre-driver are disposed on a first circuitboard and the plurality of gate drivers and the plurality of IGBTs aredisposed on a second circuit board.
 30. The IGBT circuit moduleaccording to claim 27, wherein a first subset of IGBTs is switchedduring one switching cycle and a second subset of IGBTs is switchedduring another switching cycle.